Public works machine

ABSTRACT

This invention relates to a method for adjusting the position of the working equipment with which a public works machine is provided, which is constituted by a group of front drive wheels and a group of rear drive wheels, by said working equipment which is articulated to the frame of the machine, whilst a doubleeffect drive member is coupled between the working equipment and the frame and comprises two chambers connected selectively to a source of pressurised fluid and to a discharge tank or isolated from said fluid sources and discharge tank, according to which method the working equipment is disposed in a predetermined position, isolating said two chambers, and the displacement of the machine is controlled, wherein the position of the working equipment subsequent to the predetermined position is a function of the values of the resistant torques of the groups of front and rear wheels. It also relates to a public works machine applying the method as mentioned hereinabove.

United States Patent Gautier Jan. 1, 1974 PUBLIC WORKS MACHINE Primary Examiner-Gerald M. Forlenza 75 Inventor: Joe! P. Gautier, Le Plessis-Belleville, AS34514"? i- E- France Atl0rneyNathan1el A. Humphnes et a1.

[73] Assignee: Sociele Anonyme Poclain, Oise,

France [57] ABSTRACT [22] Filed; Man 1 1972 This invention relates to a method for adjusting the position of the working equipment with which a public [21] PP N04 2351442 works machine is provided, which is constituted by a group of front drive wheels and a group of rear drive wheels, by said working equipment which is articu- [30] Foreign Application P i i D lated to the frame of the machine, whilst a double- Mar. 22 i971 France 7110033 effect drive member is Coupled between the working V H equipment and the frame and comprises two chambers connected selectively to a source of pressurised fluid 52 U.S. c1. 214/762, 214/152 and a dischafrge tank or isolated said l [51] Eozf 3/86 sources and discharge tank, according to WhlCh [58] Field of Search 214/762, 140, 152; method the wmking equipment imposed m a Wide 180/648; 173/4, 5, 6, 7 termined position, isolating said two chambers, and the displacement of the machine is controlled, wherein the position of the working equipment subse- References Cited quent to the predetermined position is a function of the values of the resistant torques of the groups of UNITED STATES PATENTS front and rear wheels It also relates to a public works 3.54:,228 11/1970 Horsch 214/762 machine applying the method as mentioned herein- 3,233,69l 2/1966 DeBiasi l80/6.48 b

1..C a s 3 aw n figure rustic WORKS MACHINE The present invention relates to a method of adjusting the position of the working equipment of a public works machine, and machine carrying out said method.

Numerous public works machines operate at present by the operating equipment being placed in position and the machine generally moving forwards. Loaders are thus known in which the bucket is disposed at ground level, the said bucket then penetrating into the material to be dug by the simple displacement of the machine. This type of operation is often called shovel work. Moreover, it is of course understood that such a mode of procedure is not reserved only for loaders.

Certain of the machines which have just been evoked have their rolling members constituted by wheels, this including the advantages inherent in this mode of propulsion. However, it has been ascertained that during operation the machine on wheels tended to tilt, depending on the circumstances, about the axle of the front wheels or of the rear wheels. In any case, the force developed by the machine in the course of its advance movement was at the most equal to the force of adherence only of the wheels still in contact with the ground. This state of affairs is considered to be a disadvantage in heretofore known machines, since the force developed by the abutment of the wheels of one axle only on the ground is insufficient in numerous cases.

The invention proposes precisely to remedy the above-mentioned disadvantages and to this end has firstly for an object a method by which a substantially permanent contact of the wheel assembly of the machine may be ensured on the ground. The invention also has for an object the machines applying the method.

The invention therefore relates to a method of adjusting the position of the working equipment with which a public works machine is provided, which is constituted by a group of front drive wheels and a group of rear drive wheels, by said working equipment, which is articulated on the frame of the machine, whilst a douhie-effect drive member is coupled between the working equipment and the frame, and comprises two chambers selectively connected to a source of pressurised fluid and to a discharge tank, or isolated from said sources of fluid and tank. According to this method, the working equipment is disposed in a predetermined position, isolating said two chambers, and the displacement of the machine is controlled.

Moreover, the position of the working equipment subsequent to the predetermined position is made to be a function of the values of the resistant torques of the front and rear groups os wheels.

The invention also has for its object a public works machine applying the above-mentioned method. This machine is constituted by a group of front drive wheels and by a group of rear drive wheels, by at least one bydraulic drive motor coupled to each group of drive wheels and connected to a source of pressurised fluid by a feed conduit, by a working equipment articulated to the frame of the machine, by a first double-effect drive member which is coupled between the working equipment and the frame and comprises two chambers, by a first and a second conduit connected respectively to said two chambers, a first distributor with at least three positions connecting, in a first position, the first conduit to a source of pressurized fluid and the second conduit to a discharge tank, connecting, in a second postion, the first conduit to said discharge tank and the second conduit to the source of pressurised fluid and isolating, in a third position, said two chambers from said tank and source of fluid.

Third and fourth conduits are connected in shunt to the first and second conduits respectively between the first drive member and the first distributor, whilst a second distributor with three positions is interposed on the third and fourth conduits between on the one hand the connections of said third and foruth conduits to the first and second conduits and, on the other hand, a source of pressurized fluid and a discharge tank, and this second distributor, in its first position, connects the third conduit to said latter source of pressurised fluid and the fourth conduit to said latter discharge tank, in its second position, connects the third conduit to the discharge tank and the fourth conduit to the source of pressurized fluid, and in its third position, isolates the first and second conduits from the source of pressurised fluid and from the discharge tank. Finally, fifth and sixth conduits are connected on the one hand to the conduits feeding the hydraulic motor or motors driving the groups of front and rear drive wheels respectively, on the other hand to the two chambers of a second drivemernber for controlling the position of the movable member of the second distributor coupled between said movable member and the body of said second distributor.

in addition, the second drive member advantageously comprises a body and an element which is movable with respect to said body, whilst an elastic element is interposed between said movable element and said body of said second drive member.

Furthermore, a third distributor is advantageously interposed on the third and fourth conduits between the connections of said third and fourth conduits to the first and second conduits, and the second distributor, whilst this third distributor has two positions, in a first position of said third distributor, the first and second conduits are connected to the inlet of the second distributor, and in the second position of the third distributor, the first and second conduits are connected to the inlet of the second distributor, and in the second position of the third distributor, the first and second conduits are isolated from said second distributor.

The first and second drive members are preferably constituted by double'effect hydraulic jacks.

The invention will be more readily understood upon reading the following description with reference to the accompanying drawings, in which:

FIGS. 1 and 2 schematically show a machine of the loading type in the course of two cases of use:

FIG. 3 shows the hydraulic circuit of a machine according to the invention.

Referring now to the drawings, a public works machine, such as a loader, may, in a first phase of use, tend to take the position of FlG. l. The machine advances, the bucket l abuts on the material 2 and does not manage to penetrate into said material. The force of reaction of the material 2 on the bucket l is transmitted, by the working equipment 3, to the frame d of the machine, the front wheels 5 of which tend to lose contact with the ground 6.

In another phase of use shown in MG. 2, it is ascer? tained on the contrary that, when for example the bucket l tends to lift all or part of the material 2, it is the rear wheels 7 of the machine which lift from the ground 6. It will further be noted that a double-effect jack 8 is coupled between the working equipment 3, which is articulated to the frame 4 about axis 9, and said frame 4. To this end, the rod of the piston of the jack is articulated to the working equipment 3 about axis 10 and the cylinder is articulated to the frame 4 about axis 11.

FIG. 3 shows the jack 8 having two chambers 12 and 13 connected to a first distributor 14 via a first conduit 15 and a second conduit 16 respectively. The distributor 14 is itself connected by conduits 17 and 18, respectively, to a hydraulic pump 19 and to a discharge tank 20. The movable member of the distributor 14 has three positions which correspond respectively, the first position to the communications of conduit 15 with conduit 17 and of conduit 16 with conduit 18, the second position to the communications of conduit 15 with conduit 18 and of conduit 16 with conduit 17, and finally, the third position, to the communication of the conduit 17 with conduit 8,. and to the isolation of conduits 15 and 16.

Also to be noted are the hydraulic motor or motors for driving the front wheels, shown at 21, and the hydraulic motor or motors driving the rear wheels, shown at 22. Each of these motors comprises two chambers that may be selectively placed in communication with a pump 23, 24, and with the discharge tank 20, by means of distributors and 26 with possibly coupled controls. These distributors are three-way distributors. They are connected on the one hand to the two chambers of each motor by two conduits, the distrubutor 25 by conduits 27 and 28 of the motor 21, the distributor 26 by conduits 29 and to distributor 26, on the other hand, to pumps 23, 24 and to tank 20, the distributor 25 by conduits 31 and 32, the distributor 26 by conduits 33 and 34. The selection of the first position of each distributor places conduits 27 and 31, 28 and 32, 29 and 33, 30 and 34 in communication; whilst the selection of the second position of these distributors places conduits 27 and 32, 28 and 31, 29 and 34, 30 and 33 in communication. Finally, the third position of the distributors 25 and 26 corresponds to the communicating of the conduits 31 and 32 and 33 and 34 to the isolation of conduits 27, 28, 29 and 30 from pumps 23, 24 and tank 20.

Furthermore, a distributor 35, also with three positions, is connected on the one hand by conduits 36, 37, respectively, to conduits l5 and 16 art, on the other hand, by conduits 38, 39 to the delivery of a pump 40 and to the discharge tank 20. In a first position, the distributor 35 places conduits 37 and 38, and conduits 36 and 39 in communication, whilst, in its second position, this distributor communicates conduits 36 and 3d and conduits 37 and 39. Finally, in the third position, the conduit 38 is placed in communication with conduit 39 and duits 36 and 37 are isolated from pump 40 and tank 20.

It will be noted that a jack in two parts is coupled to the movalbe member of the distributor 35, afirst chamber 41 of said jack, in which the piston 42 moves, being connected by conduit 43 to conduit 27 which feeds motors 21 in the sense corresponding to the forward movement of the machine, whilst a second chamber 44 of the jack, in which piston 45 moves, is connected by conduit 46 to conduit 29 which feeds motors 22 in the sense likewise corresponding to the forward movement of the machine. A spring 48 is interposed between the piston 42 and the body of the distributor 35.

Finally, it will be noted that a two way distributor 47 is interposed on conduits 36 and 37. in a first position, the distributor 47 maintains the free communication between the two parts of each of conduits 36, 37 whilst, in its second position, it isolates parts of conduits 36, 37, connected to conduits 15, A6 of the distributor 35, and places in communication the remaining parts of the conduits 36, 37, connected to the distributor 35. It is possible to select positions of distributor 47 by acting on lever 47a.

It will further be indicated that, in known manner, the conduits that may be placed in communication with the deliveries of the pumps are provided with shunt conduits 49 which are connected to the discharge tank 20 and on which a discharge valve 50 is interposed. it is also known to connect the suction of the different pumps to the tank 20 by conduits 5E.

The advantages presented by the machine that has just been described, and the progress that it represents with respect to the heretofore known machines will be more readily understood upon reading the following description of the operation of such a machine. To simplify matters, only the case of a machine moving forwards will be considered.

When the machine tends, therefore, to take the position of FIG. 1, and the force of abutment of the front wheels on the ground 6 diminishes, the resistant torque relative to said wheels 5 also diminishes. A drop pressure is noted of the fluid contained in the feed conduit 27 of the motors 21 in forward movement. If there is still a good adherence of the rear wheels 7, the pressures in the conduits 27 and 29 or 43 and 46 are notably different, so that, as a function of the sections adopted by pistons 42 and 45 and of the tightness of the spring 48, the movable member of the distributor 35 is pushed into its first position;

If the distributor 47 is itself disposed in its first position (as in FIG. 3), the pump 40, by conduits 38, 37 and 16, feeds pressurised fluid tochamber E3 of jack 8. The

rod of jack 8 tends therefore to emerge, this causing the working equipment 3 to rise and therefore the front wheels 5 to approach the ground 6. When said wheels 5 has remade contact, the resistant torque relative to these wheels increases again, and the pressure in the conduits 27 and 43 also increases. The movable member of the distributor tends to return to its intermediate position (third position). The balancing of the traction stresses which act on the two groups of front wheels 5 and rear wheels 7 has therefore been automatically and controllably effected.

Of course, it is easily understood that a similar functioning is obtained in the case of the rear wheels 7 tending no longer to be in abutment on the ground 6. It is therefore not necessary to describe in detaii the mode of action, which is very similar to that which has just been given, of the machine in this other configuration.

On the other hand, the above-mentioned servocontrol can be provisionally neutraiised as desired. This is the case where, in order to change a front wheel 5, for example, it is desired to remove this wheel 5 from the ground 7 and to keep it removed. To this end, it is sufficient to dispose the distributor 457, by acting on lever 47a, on its second position, and to isolate in this way the jack 8 from the servo-control to which it was previously subjected.

The range of difference between the pressures prevailing in the conduits 43 and 46 is adjustable by the choice of the value of the tightness of spring 48, in the same way as the range of pressures themselves may be adjusted by adapting the sections of pistons 42 and 45. The resulting functioning of the use of the machine which has been described therefore comes from an automatic control of the resistant torques acting concomitantly on the wheels of the two groups of front wheels 5 and rear wheels 7, and from automatic adjustment of the position of the working equipment 3 controlled by the values of these resistant torques. In this way, the best possible adherence of the drive wheels 5 and 7 is obtained and consequently, with a given power of the machine, the maximum force of penetration for the tool 1, without it being necessary for the driver of the machine to have to consider the momentary conditions of adherence, nor to be particularly experienced for reaction in optimum manner. The yield of the known machines is thus improved, the advantages thereof being, however, conserved, particularly the possibility of provisionally neutralising, by means of distributor 47, the servo-control device with which said machine is equipped.

I claim: i

1. A method of operating an earthworking machine of the type having an earthworking implement mounted for vertical adjustment on a supporting vehicle having front drive wheels and rear drive wheels, said method comprising the steps of driving the front and rear drive wheels to move the vehicle in a forward direction, monitoring the drive torque applied to the front drive wheels and the rear drive wheels, causing said earthworking implement to be moved upwardly in response to the detection of substantially less drive torque being applied to the front drive wheels than to the rear drive wheels and causing said earthworking implement to be moved downwardly in response to detection of substantially less torque being applied to said rear drive wheels than said front drive wheels.

2. The method of claim 1 wherein the step of monitoring the drive torque to the front drive wheels and to the rear drive wheels is accomplished by sensing the infeed pressure of hydraulic drive fluid supplied to respective hydraulic drive motors driving said front drive wheels and said rear drive wheels.

3. The method of claim Zwherein upward and downward movement of the earthworking implement is effected by providing pressurized hydraulic fluid to a piston and cylinder connected between the vehicle and the earthworking implement.

4. An earthworking machine comprising a vehicle having front drive wheels and rear drive wheels, front motor means drivingly coupled to said front drive wheels, rear motor means drivingly coupled to said rear drive wheels, an earth-working implement mounted on said vehicle and extending forwardly from said vehicle for engagement with a surface being worked, power adjusting means for adjusting the vertical height of said earthworking implement with respect to said vehicle, control means responsive to a lowering of the resistance to forward rotation of said front drive wheels to a level substantially less than the resistance to forward rotation of the rear drive wheels for actuating said power adjusting means to move said earthworking implement upwardly with respect to said vehicle and responsive to a lowering of the resistance to forward rotation of said rear drive wheels to a level substantially less than the resistance to forward rotation of said front drive wheels for actuating said power adjusting means to lower said earthworking implement with respect to said vehicle.

5. The invention of claim 4 wherein said front motor means and said rear motor means respectively comprise front and rear hydraulic motors.

6. The invention of claim 5 wherein said control means includes pressure comparing means for comparing the inlet pressure of said front hydraulic motor with the inlet pressure of said rear hydraulic motor.

7. The invention of claim 6 wherein said control means incudes a pilot valve having a movable control member, a first pressure responsive power means connected to a hydraulic power conduit extending from a source of hydraulic pressure'to an inlet on said front hydraulic motor and a second pressure responsive power means connected to a hydraulic power conduit extending from a source of hydraulic pressure to an inlet on said rear hydraulic motor, said first and second pressure responsive power means being connected to said movable control member in opposing manner whereby each pressure responsive power means tends to oppose operation of the other and a lowering of the pressure in either power conduit below the pressure in the other power conduit causes said control member to be shifted by the pressure responsive power means con nected to the power conduit having the higher pressure.

8. The invention of claim 7 wherein said power adjusting means comprises a hydraulic actuator comprising a piston and cylinder assembly connected between said earthworking implement and said vehicle, first and second conduits extending between said piston and cylinder assembly and said pilot valve, a hydraulic pressure source line also connected to said pilot valve, said movable control member including internal passageways for directing pressurized hydraulic fluid from said hydraulic pressure source line to one or the other of said conduits connected to said hydraulic cylinder when said first and second pressure responsive power means are creating an unbalanced force on said movable control member.

9. The invention of claim 8 additionally including manually operable valve means connected to said conduits between said pilot valve and said hydraulic cylinder for blocking said conduits from communication with said pilot valve.

10. The invention of claim 9 further including selectively operable valve means for providing pressurized hydraulic fluid to said first and second conduits selectively at a point between said manual valve means and said hydraulic cylinder.

1 1. A method for operating an earthworking machine of the type having an earthworking implement mounted for vertical adjustment on a supporting vehicle having front drive wheels and rear drive wheels, said method comprising the steps of driving the front and rear drive wheels to move the vehicle, monitoring the drive torque applied to the front drive wheels and the rear drive wheels, causing said earthworking imple ment to be moved vertically in response to the detection of substantially less drive torque being applied to either the front drive wheels or the rear drive wheels than is being applied to the other wheels to lower the wheels having the lower drive torque to consequently increase the drive torque of said wheels. 

1. A method of operating an earthworking machine of the type having an earthworking implement mounted for vertical adjustment on a supporting vehicle having front drive wheels and rear drive wheels, said method comprising the steps of driving the front and rear drive wheels to move the vehicle in a forward direction, monitoring the drive torque applied to the front drive wheels and the rear drive wheels, causing said earthworking implement to be moved upwardly in response to the detection of substantially less drive torque being applied to the front drive wheels than to the rear drive wheels and causing said earthworking implement to be moved downwardly in response to detection of substantially less torque being applied to said rear drive wheels than said front drive wheels.
 2. The method of claim 1 wherein the step of monitoring the drive torque to the front drive wheels and to the rear drive wheels is accomplished by sensing the infeed pressure of hydraulic drive fluid supplied to respective hydraulic drive motors driving said front drive wheels and said rear drive wheels.
 3. The method of claim 2 wherein upward and downward movement of the earthworking implement is effected by providing pressurized hydraulic fluid to a piston and cylinder connected between the vehicle and the earthworking implement.
 4. An earthworking machine comprising a vehicle having front drive wheels and rear drive wheels, front motor means drivingly coupled to said front drive wheels, rear motor means drivingly coupled to said rear drive wheels, an earth-working implement mounted on said vehicle and extending forwardly from said vehicle for engagement with a surface being worked, power adjusting means for adjusting the vertical height of said earthworking implement with respect to said vehicle, control means responsive to a lowering of the resistance to forward rotation of said front drive wheels to a level substantially less than the resistance to forward rotation of the rear drive wheels for actuating said power adjusting means to move said earthworking implement upwardly with respect to said vehicle and responsive to a lowering of the resistance to forward rotation of said rear drive wheels to a level substantially less than the resistance to forward rotation of said front drive wheels for actuating said power adjusting means to lower said earthworking implement with respect to said vehicle.
 5. The invention of claim 4 wherein said front motor means and said rear motor means respectively comprise front and rear hydraulic motors.
 6. The invention of claim 5 wherein said control means includes pressure comparing means for comparing the inlet pressure of said front hydraulic motor with the inlet pressure of said rear hydraulic motor.
 7. The invention of claim 6 wherein said control means includes a pilot valve having a movable control member, a first pressure responsive power means connected to a hydraulic power conduit extending from a source of hydraulic pressure to an inlet on said front hydraulic motor and a second pressure responsive power means connected to a hydraulic power conduit extending from a source of hydraulic pressure to an inlet on said rear hydraulic motor, said first and second pressure responsive power means being connected to said movable control member in opposing manner whereby each pressure responsive power means tends to oppose operation of the other and a lowering of the pressure in either power conduit below the pressure in the other power conduit causes said control member to be shifted by the pressure responsive power means connected to the power conduit having the higher pressure.
 8. The invention of claim 7 wherein said power adjusting means comprises a hydraulic actuator comprising a piston and cylinder assembly connected between said earthworking implement and said vehicle, first and second conduits extending between said piston and cylinder assembly and said pilot valve, a hydraulic pressure source line also connected to said pilot valve, said movable control member including internal passageways for directing pressurized hydraulic fluid from said hydraulic pressure source line to one or the other of said conduits connected to said hydraulic cylinder when said first and second pressure responsive power means are creating an unbalanced force on said movable control member.
 9. The invention of claim 8 additionally including manually operable valve means connected to said conduits between said pilot valve and said hydraulic cylinder for blocking said conduits from communication with said pilot valve.
 10. The invention of claim 9 further including selectively operable valve means for providing pressurized hydraulic fluid to said first and second conduits selectively at a point between said manual valve means and said hydraulic cylinder.
 11. A method of operating an earthworking machine of the type having an earthworking implement mounted for vertical adjustment on a supporting vehicle having front drive wheels and rear drive wheels, said method comprising the steps of driving the front and rear drive wheels to move the vehicle, monitoring the drive torque applied to the front drive wheels and the rear drive wheels, causing said earthworking implement to be moved vertically in response to the detection of substantially less drive torque being applied to either the front drive wheels or the rear drive wheels than is being applied to the other wheels to lower the wheels having the lower drive torque to consequently increase the drive torque of said wheels. 